What controls Earth’s temperature?
- Amount of energy received by the sun
- Reflection vs absorption of sun’s energy (albedo)
- The amount of energy retained by the earth’s atmosphere.
Amount of energy received by the sun
- The path of the earth around the sun and the earth’s angle vary at different time scales.
- Has been an important influence for glacial periods (every 100,000 years) over the past 500,000 years.
- Milankovitch Cycles
Amount of energy received from the sun?
- Sunspots – reflect the magnetic activity of the sun and the sun’s brightness.
- Approximately an 11-year cycle
Amount of energy reflected to space
- Albedo (reflectivity)
- Lighter things reflect more light energy
- Darker things absorb more light energy (heat)
- Creates positive feedback
- Aerosols lead to increased reflection of solar radiation (Volcanic activity -> cooling).
Amount of energy retained by the atmosphere
- The greenhouse effect: Energy is retained.
- Gases in the atmosphere trap heat (CO2, CH4, NOxs, CFCs)
Global energy balance
![diagram of global energy balance]()
What is “global temperature”?
Global surface temperature is calculated by averaging the temperatures over sea and land. Communicated as an anomaly.
![global map of surface temperature]()
What is “global temperature”?
- Many groups across the world have generated datasets of global temperature
- One example: Hansen et al. 2010 from Goddard Institute for Space Studies, NASA http://pubs.giss.nasa.gov/docs/2010/2010_Hansen_etal_1.pdf
- Different datasets from weather stations all over the world were compiled.
- Used a model to interpolate (smooth) data for land
- Use bucket (ships) and satellite measurements calibrated with ship measurements for the ocean
What would cause global temperature to change?
How do we measure atmospheric CO2?
- Dr. Dave Keeling started measuring the CO2 concentration in air in 1958
- Collected air in vacuum-cleared glass flasks and measured CO2 content
- Still measured with the method today (as well as sensors)
How do current changes compare to past climate?
- The earth is 4.54 billion years old
- The last ice age was 110,000 to 12,000 years ago, with peak glaciation 22,000 years ago
- The world looked different!
- Northern USA and Canada covered by ice (grey)
- Southern US covered by taiga (coniferous forest) and grassland
- Southern Europe was tundra
Ice cores!
![picture of ice core]()
Ice cores!
![picture of ice core in storage]()
Ice cores!
![picture of bubbles in ice core]()
Key questions in module
- What is the evidence for a changing climate?
- How do find & interpret data sources behind leading climate change indicators?
- How do we read and plot this data in a scriptable & reproducible manner?
- How do we communicate technical analysis in notebook formats that combine code, text, and visuals?
Key Data Science Objectives
- Reading data with diverse and unexpected formats
- Searching for how to solve problems
- Question 10 has more independence when addressing a question with data.
